I just booted OpenBSD 7.0 (which is a bit dated).

The find utility has print0, and xargs has -0. Notibly, xargs also has -P for running processes in parallel.

rm has both -d and -v.

The renice command appears to be able to use relative adjustments with -n.

There is a timeout command.

There is a readlink command, but no realpath (but a manual page exists for it as a system call).

Strict adherence to POSIX isn't a goal of any of the current BSDs is it?

People get "POSIX compliance" confused with "Unix certification". The first is an API you implement, the second is a rubber stamp.

All active Unix-like operating systems aim to implement the new interfaces as they're defined.

I'm confident they'd accept patches.